20s balance charger, how to get/make one?

[alcatraz]

Hi euc riders...

Upon reading that (balance) charging to 90% instead of 100% can increase the cycle life of a battery from 500 cycles to several thousand cycles has made me looking for a better charge solution for my new battery pack.

Balance chargers are usually 2-10s and most of them are 6s. What is one to do when one needs a 20s charger.

Never mind the wire harness that needs to be made. Imagine a computer ATX connector that makes it into a one step process.

I'm writing to ask about what would be a good way of balance charging a 20s battery?

 

I found a cheap and reliable 8 channel 6S charger (Radiolink CB86 plus) that I thought could maybe do 20s if I break the 20S balance leads down to four 5S leads. My fear is that the charger in essense is a parallel charger and that the voltage potential between the channels (up to 84v) would damage it. That would happen if the channels aren't isolated internally. 

The second option is to buy four 6S chargers that are individual and connect them each to a diffent 5S lead coming from the 20s battery. This solution would avoid the high voltages but it would sure be messy with so many devices working at once.  

Can you help me "make" a 20S charger that doesn't cost hundreds of dollars and that doesn't turn into 5 or more noisy boxes?

Cheers /a

[FULspeed]

Hi,

I'm not sure I understood the problem ...
If it is to have a recharge at 80 or 90%, are you aware of the existence of the small box "Charge Doctor"?

[esaj]

You're overthinking it. Just charge to 80% or 90% usually (there are chargers that can do that by stopping the charging at specific voltage, as well as Charge Doctor that works with the "standard" brick-chargers of the wheel), then occasionally (say, every 10-20 charges for example) charge to full and leave it sitting in the charger until the current drops to negligible values (like few tens of milliamps). Leave the balancing to the BMS.

[meepmeepmayer]

You seem to know much more about that stuff than I do. Question I'm wondering about, does the BMS need to support your type of balancing? Even if you add all the extra cables? Afaik the BMSes used in EUCs balance the cells only at full charge. How do you get around the BMS?

[alcatraz]

6 hours ago, FULspeed said:

Hi,

I'm not sure I understood the problem ...
If it is to have a recharge at 80 or 90%, are you aware of the existence of the small box "Charge Doctor"?

I searched for charge doctor but couldn't find anything. Do you remember where you saw it?

It doesn't solve the problem now. The weak cells will continue to accelerate their deviation from the good cells. 

It is a powerful compromise though that warrants consideration.

The best solution would be to somehow change the balancing voltage of the bms. That would be fantastic.

With the use of a balance charger you could use a bit more varying cells without risk of burning down your house. Just group them together by capacity and you're done. The euc never goes under 20% anyway, the voltage is too low to do any real riding. I have to say I'm tempted, but I havent found a convenient charging solution yet.

[FULspeed]

Sure, you can find it there:

http://hobby16.neowp.fr/buy/

 

[alcatraz]

1 hour ago, meepmeepmayer said:

You seem to know much more about that stuff than I do. Question I'm wondering about, does the BMS need to support your type of balancing? Even if you add all the extra cables? Afaik the BMSes used in EUCs balance the cells only at full charge. How do you get around the BMS?

I think you just hook it up in parallel. The external balancing leads can charge the batteries even though the bms is connected I think.

I think it's time for me to do some measuring of this bms. If I lucky I can interrupt the charging at 83v (4.15v individual average) and hopefully the balancing has started. I will check the individual voltages to see if 90% balanced charge can be achieved before ordering stuff and modding the euc.